The invention relates to a supporting disk for a supporting-disk bearing for a shaft of an open-end spinning rotor. The supporting disk has a disk-shaped basic body made of metal that is provided with a centric bore for receiving a shaft and that, on its circumference, has a ring made of plastic, said ring, with its outer surface, forming a smooth uninterrupted, essentially cylindrical running surface.
Supporting-disk bearings, such as those disclosed in U.S. Pat. No. 3,779,620, that are equipped with supporting disks of the initially mentioned type, have had excellent results in practice in the case of open-end spinning machines, because as a result it becomes possible to safely master very high rotating speeds of the spinning rotors. The supporting disks are subjected to a wear that is demonstrated by the fact that the rings made of plastic wear out over a period of time. Recent endeavors have aimed at increasing the rotating speeds of the spinning rotors even more, i.e., to above 100,000 min.sup.-1 (revolution per minute). This results in a further increase of the wear of the rings made of plastic and in a shortening of their useful life. As tests have shown, this increased wear is essentially the result of the fact that the rings made of plastic are heated more than before due to the higher speeds.
In order to reduce the heating, it has become known (see German Utility Model - DE-GM No. 84 33 579) to provide a ring groove in the outer surface of the ring of plastic that serves as the running surface. By means of this ring groove, a cooling is to be achieved, particularly in the central area of the ring in which otherwise a heat buildup would occur and in which the damage to the ring would then start. It was found that by means of a ring groove of this type, a reduction of the heating is possible. However, certain disadvantages have to be accepted with such arrangements since, on the one hand, the production of the ring groove requires an additional machining or manufacturing process and, on the other hand, the ring groove reduces the effective support surface area of the running surface resulting in an increased strain to the ring and to the shaft of the open-end spinning rotor. Under certain circumstances, it is therefore necessary that the overall breadth of the ring in such arrangements be enlarged.
An objective of the present invention is to develop a supporting disk of the initially mentioned type in such a way that, also in the case of high stresses, an increased heating in the central area of the ring is avoided, while still maintaining the smooth and uninterrupted running surface.
This objective is achieved according to preferred embodiments of the invention by providing the inner surface of the ring with a profiling that reduces the thickness of the ring in the central area as compared to the edge areas.
The invention is based, at least in part, on the recognition that by merely reducing the thickness of the ring, an increased heating can be avoided in the central area, presumably because of the fact that then the flexing work in the central area is less and the heat dissipation is improved at the same time. The thicker edge areas that have a better heat dissipation anyhow and do not heat up as much provide nevertheless that a sufficient damping is achieved by means of the ring made of plastic.
In a further development of especially preferred embodiments of the invention, it is provided that the thickness of the ring in the central area is between 1/3 to 1/2 of the thickness of the ring in the edge areas. These dimensions well comply with the requirements of damping and an avoidance of the heating in the central area. For the same purpose, it is advantageous, in a further development of especially preferred embodiments of the invention, for the breadth of the area of the ring that was reduced in its thickness to be between 1/6 to 1/3 of the overall breadth of the ring.
In a further advantageous development of preferred embodiments of the invention, it is provided that the circumferential surface of the basic body is provided with a counterprofiling that corresponds to the profiling of the inner surface of the ring so that the ring over its whole breadth connects to the circumferential surface of the basic body. This feature avoids the danger that, as a result of occurring centrifugal forces, the ring in its central area detaches itself from the basic body. In addition, the counterprofiling of the basic body results in an enlargement of the adhesion surface between the ring and the basic body so that on the whole an improved fastening is achieved.
In the case of certain preferred practical embodiments of the invention, it is provided that the inner surface of the ring is equipped with a surrounding ring groove. In a corresponding way, the circumferential surface of the basic body is equipped with a surrounding rib. In order to avoid that, during the operation, the ring is stressed excessively in the area of the reduced thickness, it is provided in an advantageous development that the bottom of the profiling extends at least approximately in parallel to the outer surface of the ring.
In a further development of certain preferred embodiments of the invention, it is provided that the basic body is made as an extruded part, preferably of an aluminum alloy. In this way the production of the basic body is cost-effective. In an advantageous further development, it is also provided that the ring is shaped onto the basic body by means of a centrifugal casting process. This results in an intimate connection between the basic body and the ring.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.